The immunologic events that lead to the development of Type 1 diabetes mellitus (T1DM) are not clearly defined. Understanding the immunologic events that lead to beta cell destruction is an important goal of mechanistic studies since they are likely to suggest rational treatment approaches. Both innate and adaptive immune responses are thought to be involved in the initiation and propagation of diabetes. Our group has previously identified abnormalities in circulating monocytes as well as an increased frequency of autoreactive CD8+ T cells in patients with Type 1 diabetes with Class I MHC tetramers. In this proposal, we plan to determine whether innate and/or adaptive immune abnormalities are present before the diagnosis of T1DM by studying these cells in peripheral blood collections from the TrialNet Natural History Study (NHS). We are requesting peripheral blood mononuclear cell samples from HLA-A2+ participants in the NHS. We will determine whether autoantibody+ relatives do or do not have these abnormalities and whether they predict progression of beta cell failure. In a substudy analysis, we will also compare the timing of innate and adaptive abnormalities so that the immunologic progression of the disease can be identified. The proposed studies involve a collaboration between the laboratories of Drs. David Hafler and Kevan Herold. This arrangement was made to ensure an efficient use of the NHS studies and to avoid waste of thawed cells - both investigators will carry out analyses on separate cell populations derived from the same sample. The data that will be obtained: relative expression of genes of inflammatory mediators and percentage and qualitative measures of CD8+ T cells, will be analyzed in collaboration with the TNCC and correlated with clinical and other immunologic parameters. PUBLIC HEALTH RELEVANCE: This proposal is to carry out analyses of innate and adaptive immune responses in participants in the TrialNet Natural History Study. We are requesting samples from autoantibody relatives of patients who do and do not progress to diabetes.